*表示所有列
##查询所有的员工信息
Select * from emp;
输入特指表里的单独列名进行查询
Select empno,ename,depton from emp;
关系运算符：=、!=、<>、>=、<=
区间：between A and B -》[A,B]
And:并且，和
Or：或者
Not：否，非
Is Not null：非空
In：在什么里面
Select * from stu where age=‘65‘ and gender=‘female‘;
+--------+-------+------+--------+
| sid | sname | age | gender |
+--------+-------+------+--------+
| S_1004 | liSi | 65 | female |
+--------+-------+------+--------+
Select * from stu where sid=‘S_1001‘or sname=‘lisi‘;
+--------+-------+------+--------+
| sid | sname | age | gender |
+--------+-------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1004 | liSi | 65 | female |
+--------+-------+------+--------+
写法一：select * from stu where sid = ‘S_1001‘ or sid = ‘S_1002‘ or sid = ‘S_1003‘;
写法二：select * from stu where sid in(‘S_1001‘,‘S_1002‘,‘S_1003‘);
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1002 | chenEr | 15 | female |
| S_1003 | zhangSan | 95 | male |
+--------+----------+------+--------+
select * from stu where sid not in(‘S_1001‘,‘S_1002‘,‘S_1003‘);
Select * from stu weher age is null;
方式一：Select * from stu where age >=20 and <=40;
方式二：Select * from stu where age between 20 and 40;
方式一：Select * from stu where gender !=’male’
方式二：Select * from stu where not gender =’male’
方式三：Select * from stu where gender <> ’male’
Select * from stu where sname is not null;
原文：https://www.cnblogs.com/gwl1027/p/14682310.html